The present invention relates to the direct writing of materials. More particularly, the present invention pertains to methods of direct writing low carbon conductive materials, e.g., low carbon platinum.
Focused beam systems, e.g., focused ion beam (FIB) systems, can be used in forming, shaping, or altering microscopic structures in semiconductor devices. The focused ion beam is directed to a small point on a semiconductor device and then scanned, in a raster fashion, over a particular area where material is to be removed or deposited. In removal of material, as the ion beam impinges upon the semiconductor device surface, momentum of the ions is transferred and can result in the removal of one or more surface atoms. By selecting a raster pattern of a given overall shape, for example, a horizontal raster pattern, a correspondingly shaped area of surface material can be removed.
In the deposition of material, for example, a particular metal containing compound, e.g., a gaseous precursor, is provided in the system. A metal material may be deposited upon a specific area of a surface by directing an ion beam toward the surface simultaneously with the introduction of the gaseous precursor. The beam directed towards the surface in the presence of the gaseous precursor forms the material on the surface.
Such direct writing using focused ion beam techniques has been used to deposit material such as patterns for semiconductor applications, has been used to correct patterns of devices, and has been used for other general semiconductor applications. For example, platinum may be deposited in specific areas on a surface defined by the focused ion beam, e.g., line repair. Further, for example, such platinum may be deposited using a platinum precursor of MeCpPtMe3 (where Cp=cyclopentadienyl). However, metals like platinum directly written using FIB techniques or by conventional chemical vapor deposition (CVD) are generally high in carbon content.
Chemical vapor deposition is generally defined as the formation of a non-volatile solid layer or film on a substrate by the reaction of vapor phase reactants that contain desired components. The vapors are introduced into a reactive vessel or chamber, and decomposed and/or reacted at a heated surface on a wafer to form the desired layer. Chemical vapor deposition is but one process of forming relatively thin layers on semiconductor wafers, such as layers of elemental metals or compounds. For example, a compound, typically a heat decomposable volatile compound (also known as a precursor), is delivered to a substrate surface in a vapor phase. The precursor is contacted with a surface which has been heated to a temperature above the decomposition temperature of the precursor. A coating or a layer forms on the surface. The layer generally contains a metal, metalloid, alloy, or mixtures thereof, depending upon the type of precursor and deposition conditions employed. For example, CVD of platinum is described in the article entitled xe2x80x9cCharacterization of Pt Thin Films Deposited by Metallorganic Chemical Vapor Deposition for Ferroelectric Bottom Electrodes,xe2x80x9d by Kwon et al., J.ElectroChem.Soc., Vol. 144, No. 8 (August 1997).
Precursors typically used in CVD are generally organometallic compounds, where a hydrocarbon portion of the precursor functions as the carrier for the metal or metalloid portion of the precursor during vaporization of a liquid precursor. For microelectronic applications, it is often desirable to deposit layers having high conductivity, which generally means the layer should contain minimal carbon and oxygen contaminants. However, one problem of a CVD deposited layer formed from an organometallic precursor is incorporation of residual carbon from the hydrocarbon portion of the precursor. Further, oxygen that may be present in the atmosphere during deposition may also be problematic. For example, oxygen incorporation into the layer before or after deposition generally results in higher resistivity. Further, it is also believed that organic incorporation (such as pure carbon or hydrocarbon) into the resultant deposited material reduces density and conductivity. A low density layer can subsequently lead to oxygen incorporation into the layer when it is exposed to ambient air. Yet further, CVD deposited layers are not useful in line repair.
Conductive material can be used in the fabrication of various integrated circuits and for repair thereof. For example, conductive materials are used as electrodes for storage cells of memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and even ferroelectric (FE) memory devices. Generally, high quality layers of metals are required for semiconductor applications. To be effective conductive materials, low resistivity is generally desired. Therefore, layers having low carbon and/or low oxygen content are desired. Further, various other applications also require such low resistivity conductive layers, e.g., contacts, interconnects, repair lines, etc.
Therefore, what is needed are methods for forming substantially carbon-free and/or substantially oxygen-free conductive material useful for semiconductor applications. For example, such a conductive material, e.g., low carbon and/or low oxygen platinum, formed using focused beam techniques may be used as a conductive material for line repair or in the formation of patterns in the fabrication of semiconductor devices, e.g., capacitor structures, interconnects, contacts, etc.
A method for providing a conductive material includes providing a substrate assembly having a surface and providing a stream of platinum containing precursor to a region proximate the surface of the substrate assembly where platinum is to be deposited. Further, a stream of oxygen containing gas is provided to the region proximate the surface of the substrate assembly where the platinum is to be deposited. A focused beam is directed towards the surface of the substrate assembly in the presence of the stream of platinum containing precursor and the stream of oxygen containing gas in the region proximate the surface of the substrate assembly to deposit the platinum on the surface.
In one embodiment, the platinum containing precursor includes a precursor selected from the group of MeCpPtMe3 (where Cp=cyclopentadienyl), CpPtMe3, Pt(acetylacetonate)2, Pt(PF3)4, Pt(CO)2Cl2, Pt hexafluoroacetonate, and cis[PtMe2(MeCN)2]. Further, in another embodiment, the stream of oxygen containing gas includes a stream of at least one gas selected from the group of O2, O3, NO, N2O, H2O2, and R2O2 (where R is any organic group that does not interfere with the deposition of the conductive material).
In another method for forming platinum according to the present invention, the method includes providing a substrate assembly having a surface in a chamber and providing a stream of platinum containing precursor to a region proximate the surface of the substrate assembly where platinum is to be deposited. The stream of platinum containing precursor is provided at a flow rate of about 0.01 sccm to about 10 sccm. Further, a stream of oxygen containing gas is provided with the stream of platinum containing precursor to the region proximate the surface of the substrate assembly where the platinum is to be deposited. The stream of oxygen containing gas is provided at a flow rate of about 0.001 sccm to about 10 sccm. The chamber is maintained at a temperature in a range of about 20xc2x0 C. to about 300xc2x0 C. and at a pressure in a range of about 10xe2x88x925 torr to about 10xe2x88x929. A focused beam is scanned over the surface of the substrate assembly in the presence of the stream of platinum containing precursor and the stream of oxygen to deposit the platinum on the surface.
Further, a method for providing a conductive metal material is also provided. The method includes providing a substrate assembly having a surface and providing a stream of a precursor containing conductive material to a region proximate the surface of the substrate assembly where the conductive material is to be deposited. A stream of reaction gas is also provided to the region proximate the surface of the substrate assembly where the conductive material is to be deposited. The reaction gas is one of an oxygen or hydrogen containing gas. A focused beam is scanned over the surface of the substrate assembly in the presence of the stream of precursor containing conductive material and the stream of the reaction gas to deposit the conductive material on the surface.
In one embodiment, the stream of the precursor containing conductive material includes a stream of a precursor containing one of platinum, palladium, rhodium, ruthenium, chromium, silver, and iridium. Further, the stream of the reaction gas includes providing a stream of a reaction gas including at least one gas selected from the group of H2, NH3, O2, O3, NO, N2O, H2O2, and R2O2.
A method for line repair according to the present invention includes providing a substrate assembly having a surface including a first conductive region and a second conductive region. The first and second conductive regions are separated by a line repair region upon which platinum is to be formed to connect the first conductive region to the second conductive region. A stream of platinum containing precursor is provided to the line repair region proximate the surface of the substrate assembly where platinum is to be formed along with a stream of oxygen containing gas. A focused beam is directed towards the surface of the substrate assembly in the presence of the stream of platinum containing precursor and the stream of oxygen containing gas in the line repair region to form platinum on the surface for connection of the first conductive region to the second conductive region.